The present invention is related to sensing temperature and is more particularly related to sensing temperature of an electronic chip at the chip level.
U.S. Pat. No. 5,213,416 issued May 25, 1993 to Neely et al. for ON CHIP NOISE TOLERANT TEMPERATURE SENSING CIRCUIT discloses an on-chip temperature sensing circuit which includes a differential voltage source (DVS) having first and second branches, each branch having thermal sensitive transistor connected in series with a current source, amplifiers coupled to the output nodes of first and second branches of DVS, and a means for generating an on-chip voltage signal at an output electrode of chip which provides a voltage signal indicative of the temperature of the chip.
U.S. Pat. No. 5,639,163 issued Jun. 17, 1997 to Davidson et al. for ON-CHIP TEMPERATURE SENSING SYSTEM discloses an on-chip temperature sensing system which includes first and second thermal sensing diodes interconnected with a common cathode to supply to form a differential sensing pair formed on a chip, a power supply disposed apart from chip, a first precision resistor coupling power provide a first current of a predetermined magnitude, a second first thermal sensing diode to precision resistor coupling power supply to thermal sensing diode to provide a second current of a predetermined magnitude, and means to couple the anode of first thermal sensing diode to the anode of second thermal sensing diode as differential inputs to a high impedance amplifier.
U.S. Pat. No. 5,154,514 issued Oct. 13, 1992 to Gambino et al. for ON-CHIP TEMPERATURE SENSOR UTILIZING A SCHOTTKY BARRIER DIODE STRUCTURE discloses an on-chip temperature sensor which includes a diode structure including a silicon substrate, a first region of a metal silicide in silicon substrate, a second region of a metal-oxide semiconductor material on first region, a third region of a metal over second region and means using said diode structure as a temperature sensitive device for measuring an ambient temperature.
Japanese patent JP7074218A published Mar. 17, 1995 by Tamotsu Naganuma for TEST METHOD OF IC AND ITS PROBE CARD discloses temperature of the IC chip is monitored directly by a method wherein a temperature sensor probe is brought into contact with the surface of an IC chip.
Japanese patent JP58073145A published May 2, 1983 by Hiroyuki Futaki for SEMICONDUCTOR PACKAGE discloses a method for measuring temperature of the chip wherein a temperature sensor is built in the package which senses the temperature of the chip directly.
U.S. Patent application Publication 2001/0026576A1 published Oct. 4, 2001 by Beer et al. for METHOD FOR DETERMINING THE TEMPERATURE OF A SEMICONDUCTOR CHIP AND SEMICONDUCTOR CHIP WITH TEMPERATURE MEASURING CONFIGURATION discloses a method for determining a temperature of a chip which includes impressing a defined current onto selected chip terminals, measuring a voltage occurring at least partially at a semiconductor diode disposed between the selected chip terminals using four-conductor connection technology, and determining the temperature of the chip by reference to the voltage and the defined current.
Japanese patent JP2023645A published Jan. 25, 1990 by Masaaki Uno for SEMICONDUCTOR INTEGRATED CIRCUIT discloses measuring chip temperature by mounting a temperature sensor detecting the chip temperature of a semiconductor integrated circuit by means of the drain current of a MOS transistor at a state in which a prescribed voltage is impressed between a gate electrode and source/drain regions of the MOS transistor.
Japanese patent JP63000132A published Jan. 5, 1988 by Akiyoshi Takeyasu for WAFER TESTING UNIT discloses determining the surface temperature of a wafer and chip by incorporating probe needles and a novel temperature sensor for detecting a chip temperature, and providing a control box controlling the temperature sensor.
Japanese patent JP11211792A published Aug. 6, 1999 by Junichi Seki for PROTECTION DEVICE OF SEMICONDUCTOR-TESTING DEVICE discloses measuring chip temperature directly by forming a diode on a silicon chip as a temperature sensor, and measuring forward characteristics of the diode.
The present invention provides for accurately and inexpensively measuring chip temperatures by a combination of on-chip temperature sense elements, Kelvin connection, and calibration.
The present invention provides for measuring the temperature of a chip while in operation. The present invention further provides for measuring chip temperature accurately. The present invention further provides for minimizing the cost of accurately measuring the temperature of a chip while in operation.
An object of the present invention is to minimize the thermal resistance between the thermal sensor and the chip being monitored. This is accomplished by measuring the resistance of a metallic coil located directly on the chip. The coil is essentially the same temperature as the chip.
It is also an object of the present invention to provide a unique calibration scheme which takes advantage of the resistance versus temperature characteristics of metallic coil. These characteristics translate to a mathematical straight line y=mx+b. Substituting resistance and temperature values results in
t=m(Rxe2x88x92r)+R
Where:
m is the mathematical slope which models the physical characteristics of the metallic coil""s inherent resistance versus temperature characteristics.
R is the resistance of the coil at a given known temperature such as room temperature. R is the calibrated resistance of a measured metallic coil resistance versus measured temperature.
(Rxe2x88x92r) is the resistance change of the coil from its room temperature resistance.
t is the calculated temperature of the coil and thus the temperature of the chip.
Calibration proceeds by determining R. To accomplish this requires the coil to be at a known temperature and then measuring its resistance. With the system powered off, the cooling system is allowed to blow room temperature air across the chip. While this is in progress, the resistance of the coil is monitored. The coil is determined to be at room temperature when its resistance becomes stable i.e. stops changing. At this point the coil is at the same temperature (room temperature) as the air being moved across it. The power system now measures the room temperature at the air input to the cooling system used to cool the chip. The resultant is a known resistance R at a known temperature. The calibration data is stored for use in dynamic calculations of the chip temperature.
It is a further object of the present invention to provide an accurate, inexpensive resistance measurement. Resistance is measured by forcing a voltage and measuring the resulting current. Each power supply contains a measurement circuit and is connected to a dedicated chip coil. This allows each supply to monitor chip temperature. Accuracy is achieved by a variable output forcing voltage to maximize signal strength for the particular measurement conditions. During the calibration phase (unbiased phase) less forced voltage can be tolerated, as opposed to the powered state during normal measurement where a higher voltage can be supported after chip bias has been applied. Since the higher forced voltage can induce self heating and alter the coil resistance, duty cycle is controlled on the forced voltage that can be as little as 3% to get high signal strength without inducing self heating
An inexpensive solution is achieved by using a single base circuit and multiplexing multiple metallic coils. Due to the already enforced duty cycle limit, many coil elements can be measured seemingly simultaneously by time sharing the base circuit. Multiplexing in a fixed known resistance (test point resistance) also adds accuracy, and error detection, since the known resistance validates the base circuit is working properly and within tolerance.